Circuit breaker



April 28, 1931. N. s. NE LSON,

` CIRCUIT BREAKER Filed April 16, 1926 4 1 a k j INVENTOR. /lZ &Mima

A TTORNEY.

Patented Apr. 28, 1931 UNITED STATES PATENT OFFICE NELS S. NELSON, OF PONTIAC, MICHIGAN, ASSIGNOR, BY MESNE ASSIGNMENTS, TO SAFETY TIRE 'POP-VALVE COMPANY, A COBPORATION OF MICHIGAN cmcurr :BREAKER Application filed April 16,

The primary object of my invention is to provide a circuit breaker for electrical circuits which will automatically break the circuit upon being subjected to an over-load of current, and while it will intermittently and momentarly reestablish the current if such over-load continues over a period of time, it will maintain such circuit in substantially continuously broken condition, and will again continuously close the circuit when such overload is relieved.

It is a further object of my invention to y provide in an electric circuit, a circuit breaking link which cannot readily be melted, and so destroyed, but which will function for an indefinite time without replacement.

' With these and other objects in view, my invention consists in the arrangement, combination and Construction of the various parts of my improved device-as described in the specification claimed in my claims and shown in the accompanying drawing, in which:

Fig. 1 is a sectional view of an automatic electric fuse plug embodying my invention.

Fig. 2 is a sectional View of a fuse Cartridge embodying a modification of my invention.

Fig. 3 is a sectional view of a fuse Cartridge' adapted for use in a knife type switch, em-- bodying another modification of my invention.

I have shown in Fig. 1, a plug having body portion 2 of porcelain, glass, rubber 'or other insulating material, a metal cap 1 fitting over the open end of the body portion 2, a metal screw shell 3 covering body 2, a metal rivet 4: secured in the lower end of body 2, a portion of'said' screw shell being extended to the interior of body 2 as at 6, a thermostatic metal contact link 5 secured b an end in metal rivet 4 by solder 7, ma ing contact with its other end at solderedsurface 6 of extendin and overlapping portion of screw shell 3.7 he extending and overlapping portion of screw shell 3 ending at its soldered surface 6, is inserted through' opening in body 2 as shown, and secured in said opening by a filling of wax 8. The contact link 5 is constructed of two specially prepared metals welded together in horizontal layers, one of 1926. Serial No. 102366.

said welded metals having a very low rate of expansion, and the other having a very high rate of expansion, and both being capable of being'heated to a very high degree and rapidly cooling without melting or losing torsion. Therefore, When an overload of electric current passes through screw shell 3 to contact link 5 to metal rivet 4, the metals comprising the contact link 5 will become heated by the excessive current and the layer of metal 'having a high rate of expansion will expand more rapidly than the layer of metal having the low rate of expansion andcause the link 5 to bend its free end away from the contact surface 6, as shown in the dotted lines, thereby breaking the circuit. When the circuit is broken the metals forming the link 5 will rapidly cool and permit the link 5 to return to rest in contact with the surface 6, thereby reestablishing the circuit.

InFig. 2 I have shown a Cartridge fuse having a tube 10 of fibre, glass, rubber or other suitable insulating material, metal caps 9 and 11 covering and secured to the ends of the tube 10, contact link 13 of same materials as compose link 5 of Fig. 1 secured to center of metal cap 9 by metal plate 12 and extend- -ing within insulating tube 10, contact link 14=composed of same materials as link 13, secured to center of metal cap 11 by metal late 15, and extending within insulating tu e` 10 to meet and make free contact with link 13. Contact links 13 and 14 upon being subjected to an overload of electrc current, become heated and rapidly expand, and in expanding bend as explaned in connection with link 5, and separate from each other at contact point thus breaking the circuit. When the circuit is thus broken the links 13 and 14 will rapidly cool and return to normal positions of rest in contact with each other, thereby reestablishing the circuit.

In Fig. 3 I have shown a type of Cartridge fuse adapted to use in a knife type fuse block which is of the same Construction as Fig. 2 except that the inverted T shaped metal 16 adapted to fit knife type fuse block 'is added, and is secured to metal cap 17 by the overlapping edges thereof, substantially as shown. The contact links contained in car tridge shown in Fig. 3 are of the same type and Construction as shown in Fig. 2, and function in the manner already described.

The use of my improved device obviates the necessity of replacng a fuse plug or fuse Cartridge each time the circuit in which it is connected is subjected to an overload of current, as my contact link, which is substi- 'tuted for the usual fusible link, is not melted by the heat generated by the overload of current, but is merely rapidly expanded by such heat, and in expanding sprngs away from its contact point, and thereby breaks the circuit. The contact link immediately upon being relieved of the heat generated by the overload, rapidly cools and resumes its normal position and reestablishes the circuit.

It is obvious that various changes may be made in the arrangement, combination and Construction of the various parts of my improved device without departing from the spirit of my inventon, and it is my intention to cover b my claims such changes as may be reasona ly included within the scope there- What I claim is:

1. As an article of manufacture, a circuit breaker for an electrical circuit comprising a nonconductive tubular member, conductive members covering the ends of said tube, a pair of bimetallic conductors each composed of elements having unequal coeflicents of expansion positioned within said tube and each having an end secured to one of said con: ductive end members and having their free ends normally in contact within said tube and free to break said contact upon expansion.

2. As an article of manufacture, a circuit breaker for an electrical circuit comprising a nonconductive tubular member, conductive members coverng the ends of said tube and having exterior knife-'like extensions, a pair of bimetallic conductors each composed of elements having unequal coeflicients of ex- Eansion positioned within said tube and each aving an end secured to one of said conductive end members and having their free ends normally in contact within said tube and free to break said contact upon expansion.

e NELS S. NELSON. 

